This project is proposed to identify and investigate potential effects of pulsed wave, low power diode (LPD) laser irradiation on selected biochemical processes in intact human cells. Various sources of anecdotal experience as well as a few clinical and basic science reports (mostly from Russia and Eastern Europe) suggest that LPD lasers may exert biostimulation of cell growth and metabolism, thereby facilitating various healing processes. On the other hand, few physico-chemical and biological reports relating to such effects have appeared in the English literature. Since this variety of evidence has produced relatively "soft" data, a more systematic evaluation is needed in order to define experimental conditions for producing biostimulation with laser irradiation. Gallium-aluminum-arsenide lasers emit irradiation in the near infra-red (904 nm), a wavelength which effectively penetrates cells and tissues. However, the energy of these lasers are orders of magnitude less than the more commonly used lasers for surgery, destruction of neoplastic tissue, and other highly invasive procedures. The specific aims of the project include investigations of cell growth, cell membrane transport, respiratory capacity, and biosynthetic processes as effected by pulsed LPD laser irradiation. All experiments will utilize cultured human fibroblasts. A custom built laser having the capabilities of modifying pulse height, width and frequency has been constructed and calibrated; it is available for this project. It will be utilized to pulse irradiate growing fibroblasts under varying conditions. Once an irradiation effect is observed, optimum conditions will be sought as a first step toward elucidating this effect. As soon as preliminary observations establish conditions for eliciting a radiation-induced biostimulation, more intensive and extensive investigations would be planned.